This invention relates to metered dose inhalers with the specific intent for a reliable valve mechanism which will prevent inhalation of air until just prior to medication injection by the unit into the inhaled air stream without alteration of the medication spray in any way.
Millions of persons with asthma, chronic obstructive pulmonary disease, emphysema, and other pulmonary problems use metered dose inhalers for the administration of nebulized medications of various types into their lungs. Timing between the beginning of the inspiration of air to the injection of the nebulized medication is critical. Injection of medication to late deposits the medication in the mouth and throat. Injection to early carries the medication into the smallest air sacs of the lung, the alveoli, which in most cases is not desirable. The correct timing deposits the medication in the trachea, bronchi, and bronchioles. In all current metered dose inhaler units, there is an open breathing passage around a medication canister which must be depressed, against spring pressure, about 0.080 inches to begin medication injection, inspiration by the patient to begin at about 0.060 inches of movement. It is virtually impossible, even with training, to achieve perfect timing. As a result, pharmacists speculate that up to 50% of medication is wasted.
Devices such as described by Larson, et al, U.S. Pat. No. 5,598,836 allow air leakage at all times. Actually, huge quantities of air can be inhaled through minute openings before the medication spray which is not desired by pulmonary physiologists. The case is a complex mechanical device with no protection for the canister, a highly specialized device which would be expensive to manufacture and would require F.D.A. approval as a drug.
The mechanism of Hause, U.S. Pat. No. 5,904,139 is again a complex specialized case with vent holes sealed by a plunger seal which is held in place by either pressure of the internal spring mechanism of the medication canister, or by a separate spring which is placed above or below the canister which defeats the timing. The unit of Hause appears not to be reusable hence refill canisters, which are less costly than whole new units, could not be used. The unit would also appear to be non cleanable which is contrary to the desires of all manufacturers of metered dose inhalers and physicians prescribing them. It would also require F.D.A. approval as a drug.
Another device of a whole different nature, a spring loaded means which has to be cocked, with a button to press that triggers the opening of a flap valve and depresses the canister, is a highly specialized, expensive to construct means with many parts to fail, and this has not been a popular addition to the field.
No prior art has been able to utilize the actuator cases that are now in common usage.
In accordance with the present invention, an insert valve comprises a tubular mounting means, with a lateral opening for medication spray, a cup like well holding a top plate with peripheral air passages and a central opening for medication delivery means, said top plate extending to the walls of the medication canister case and which by means of a flexible elastic diaphragm with a central opening and a wipe seal in the cup, prevents air passage until the medication canister is depressed, opening the air passages just prior to medication spray.
Accordingly, several objects and advantages of my invention are an inexpensive, foolproof insert valve which can be molded to fit into any commonly used metered dose inhaler actuators currently in use with rare exception. It will effectively time inspiration to medication injection into the inhaled air stream and is self closing, not relying on the medication canisters internal retracting means. It will allow the medication canister to be removed for complete cleaning of the actuator, the removeable flexible diaphragm being easily reinserted. It may be used with more than one refill medication canister further saving expense. It does not allow leakage of air prior to activation, highly desired by pulmonary specialists, nor does it in any way interfere with medication dosage, plume velocity or shape, medication particle size, or air velocity around the medication spray. Another obvious advantage is that the metered dose inhaler is not changed in appearance or use. The user depresses the canister top as he or she has always done.